Re: [PATCH/WIP 1/8] wrapper: implement xopen()

[Stefan Beller <sbeller@google.com>]

On Wed, May 27, 2015 at 6:33 AM, Paul Tan <pyokagan@gmail.com> wrote:
> A common usage pattern of open() is to check if it was successful, and
> die() if it was not:
>
>         int fd = open(path, O_WRONLY | O_CREAT, 0777);
>         if (fd < 0)
>                 die_errno(_("Could not open '%s' for writing."), path);
>
> Implement a wrapper function xopen() that does the above so that we can
> save a few lines of code, and make the die() messages consistent.

As a mental todo note for whomever wants to pick up some work: This patch
series indicates to only touch git-am. The first 2 patches introduce
new x-wrappers,
so maybe we'd need to grep through the whole code base and convert the all
these file opening code to the new wrapper.

>
> Signed-off-by: Paul Tan <pyokagan@gmail.com>
> ---
>  git-compat-util.h |  1 +
>  wrapper.c         | 18 ++++++++++++++++++
>  2 files changed, 19 insertions(+)
>
> diff --git a/git-compat-util.h b/git-compat-util.h
> index 17584ad..9745962 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -718,6 +718,7 @@ extern char *xstrndup(const char *str, size_t len);
>  extern void *xrealloc(void *ptr, size_t size);
>  extern void *xcalloc(size_t nmemb, size_t size);
>  extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
> +extern int xopen(const char *path, int flags, mode_t mode);
>  extern ssize_t xread(int fd, void *buf, size_t len);
>  extern ssize_t xwrite(int fd, const void *buf, size_t len);
>  extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);
> diff --git a/wrapper.c b/wrapper.c
> index c1a663f..971665a 100644
> --- a/wrapper.c
> +++ b/wrapper.c
> @@ -189,6 +189,24 @@ void *xcalloc(size_t nmemb, size_t size)
>  # endif
>  #endif
>
> +/**
> + * xopen() is the same as open(), but it die()s if the open() fails.
> + */
> +int xopen(const char *path, int flags, mode_t mode)
> +{
> +       int fd;
> +
> +       assert(path);
> +       fd = open(path, flags, mode);
> +       if (fd < 0) {
> +               if ((flags & O_WRONLY) || (flags & O_RDWR))
> +                       die_errno(_("could not open '%s' for writing"), path);
> +               else
> +                       die_errno(_("could not open '%s' for reading"), path);
> +       }
> +       return fd;
> +}
> +
>  /*
>   * xread() is the same a read(), but it automatically restarts read()
>   * operations with a recoverable error (EAGAIN and EINTR). xread()
> --
> 2.1.4
>